The present invention generally relates to a electronic microcircuitry, and, more specifically, to the fabrication of superconducting microcircuitry.
From their advent in the late 1950's-early 1960's, conventional microcircuitry has revolutionized the electronics industry. Electronic circuits, which in the past had been either wired point to point or on a printed circuit board, could now be generated on a chip not much larger than the size of a postage stamp. Additionally, since mass production techniques were applicable, the cost of the chips was originally much lower than more conventional circuitry, and the prices have continued to fall over time.
Of course, microlithography is now in widespread use in the fabrication of silicon based microcircuitry, a technology that has brought about a revolution in all areas of electronics. Although the fabrication process is detailed and exacting, it allows the fabrication of intricate electronic circuits, containing thousands of components, within the constraints of a small chip.
With the discovery of the new high temperature superconducting compounds in 1986, scientific interest turned immediately to developing commercial applications for the compounds. Of all the possibilities for use of the new compounds, the one which should garner the greatest enthusiasm would seem to be their application to microcircuitry, as it would engender a revolution in electronics perhaps even more monumental than that caused by the silicon based technology. However, developing this application has proved to be a daunting task, primarily because of difficulties in laying thin superconducting films and in finding compatible insulating materials.
Only recently have Josephson junction devices been fabricated on a thin film. One process for creating such a thin film Josephson junction device involves the epitaxial build-up of three layers, superconductor, insulator, superconductor. This build-up of layers is followed by ion milling techniques to cut the device out of the layers. A second technique involves the growth of epitaxial layers oriented at large angles (approximately 45.degree.). Proper selection of material type and growth conditions allows fabrication of a device. Both of these processes are cumbersome and costly, and do not lend themselves to miniaturization or high device density. In the present state of these processes, only a limited number o f devices can be fabricated on a single chip.
Recently, a new semiconducting phase was discovered in the high temperature superconducting system, Y-Ba-Cu-O. This relatively new phase is Ba.sub.2 Cu.sub.3 O.sub.5+x (0&lt;x&lt;1). This semiconducting material was first reported in 1989. The important aspect of this discovery for the present invention is that Ba.sub.2 Cu.sub.3 O.sub.5+x reacts with Y.sub.2 O.sub.3 to form the high temperature superconducting composition of YBa.sub.2 Cu.sub.3 O.sub.7-x. When Ba.sub.2 Cu.sub.3 O.sub.5+x is reacted with Pr.sub.2 O.sub.3, an insulator, PrBa.sub.2 Cu.sub.3 O.sub.7-x, is formed. Thus, this semiconducting phase, Ba.sub.2 Cu.sub.3 O.sub.5+x, is an excellent precursor for the production of superconducting devices on chips.
It is therefore an object of the present invention to provide superconducting devices using microlithography.
It is a further object of the present invention to provide patterns of either superconducting material or insulator material.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.